13,697
edits
Changes
Wine
,no edit summary
''Lactobacillus plantarum'' has been found to produce 3-sulfanylhexan-1-ol (3SH) from precursors in wine (3SH-S-cys and 3SH-S-cysgly) at a more efficient rate than wine yeast. 3SH is a volatile thiol that has a grapefruit-like flavor and aroma and is considered to be an important flavor component of some wines <ref>[http://sci-hub.hk/https://www.sciencedirect.com/science/article/pii/S0308814618305594 Impact of Lactobacillus plantarum on thiol precursor biotransformation leading to production of 3-sulfanylhexan-1-ol. Hideki Takasea, Kanako Sasakib, Daiki Kiyomichib, Hironori Kobayashia, Hironori Matsuoa, Ryoji Takatab. 2018. Doi: https://doi.org/10.1016/j.foodchem.2018.03.116.]</ref>. 50 ppm of total SO<sub>2</sub> can inhibit the growth of lactic acid bacteria in finished wine <ref>[https://psuwineandgrapes.wordpress.com/2018/10/26/understanding-difficult-malolactic-fermentations/ Dr. Molly Kelly. "Understanding Difficult Malolactic Fermentations". Wine & Grapes U. 10/26/2018. Retrieved 11/22/2018.]</ref>, although some species/strains require between 100-256 mg/L total SO<sub>2</sub> in order to be inhibited (see [[Pediococcus#Sulfur_Dioxide|''Pediococcus'']]) <ref name="Wade_2018">[https://onlinelibrary.wiley.com/doi/full/10.1111/ajgw.12366 Role of Pediococcus in winemaking. M.E. Wade, M.T. Strickland, J.P. Osborn, C.G. Edwards. 2018. DOI: https://doi.org/10.1111/ajgw.12366.]</ref>.
Lactic acid bacteria are often suppressed by yeast fermentation, which is caused in part by the yeast consuming nutrients. Very low levels of alcohol (1.5%) have been shown to stimulate early growth of LAB, but growth and MLF begin to become inhibited around 6% ABV. Yeast produce SO<sub>2</sub>, which can also inhibit LAB. However, other studies have suggested that alcohol, SO<sub>2</sub>, and low nutrients are not the only suppressors to LAB. Studies have also shown that there can be an antagonistic relationship between ''O. oeni'' and ''[[Pediococcus]]'' in wine, which may be due to toxins produced by one that affects the other known as "bacteriocins". Bacteriocins have been proposed to winemakers by scientists as a way to reduce the populations of unwanted lactic acid bacteria , although further research is needed to perfect this approach to winemaking <ref name="Wade_2018" />.
The pH of the wine can have an impact on which lactic acid bacteria species will grow. Below a pH of 3.5, ''O. oeni'' is the most dominant LAB species. ''Lactobacillus'' and ''Pediococcus'' are more common in wines above a pH of 3.5, with ''Pediococcus'' being most common in wines with a pH between 3.8 and 4.0, although ''Pediococcus'' has also been found in wines with a pH as low as 3.2 <ref name="Wade_2018" />.